New theory on the cause of the infamous Tunnel Vision problem - Testers needed!

[3lectr1cPPC]

Updated!
https://macdat.net/cap_reference.html (you may need to refresh the page on your browser for the changes to show)
Here's the Duo 250 specific page: https://macdat.net/cap_reference/apple/powerbook/duo250.html

 

[Powerbook27364]

Great to see! Hopefully the 280 won’t take too long to arrive and then I will be able to recap and provide those values. Should have the same logic board as the 280c as well.

Keep up the great work on the website!

 

[3lectr1cPPC]

Thanks! I'm at this point 99% positive that the 280/280c Logic Board uses the same cap values as the 2300 does (which I have) but it will be very good to confirm, and to have the reference photos for that system too. When I went through the web on a big spree to find PowerBook cap values a few months back, there wasn't a whole lot on the Duos. Good to see that being filled in on the site.

 

[Powerbook27364]

I’m going to order them on the chance that they are the same. That would save me several weeks of shipping times if they are. In any case, they will be confirmed when I get the duo. Hopefully all goes well. Thanks for all the help and info.

 

[3lectr1cPPC]

No problem, I'm here to help. Good luck!

 

[mdeverhart]

but it doesn't seem to be showing any signs of power when plugged in. Any ideas on what the cause may be?

Try pushing the power button on the back of the machine, rather than the one above the keyboard. Try it a couple of times if it doesn’t start up after the first time. The power button above the keyboard is a “soft” power button that goes to the Power Manager, so it only works if the Power Manager is alive. If the PRAM battery is dead (and it almost certainly is), then the Power Manager won’t be in a good state and won’t respond to the power button above the keyboard. The power button on the back effectively forces power on, which will let the Power Manager wake up from the AC adapter power, and then you should be good until the power adapter is unplugged.

The caps almost certainly need to be replaced, so shut it down and disconnect the AC adapter if you hear any unexpected “ticking” noises from the left hand side of the keyboard (that’s where the power regulators are, and a “ticking” noise likely indicates that there’s a short somewhere that’s causing the regulators to turn on/off as they hit their overcurrent limit).

 

[twelvetone12]

So I was lurking on this thread just yesterday while I was going to pick up a "for parts" Powerbook 100, thanks @3lectr1cPPC for the resources! I will dive in recapping this thing, I hooked it up to my bench supply and it does chime, but as expected the screen is blank.

 

[Powerbook27364]

No problem, I'm here to help. Good luck!

Just received the capacitor values from him to ensure they are the same, and noticed one difference. The capacitor that is noted as 330uf 16v on your site was 330uf 18v on his duo.

Unfortunately, the power button at the back doesn’t do anything either.

 

[3lectr1cPPC]

Hmm. Strange. I'll add a note about it.

 

[3lectr1cPPC]

Can you double-check with your friend that he didn't just make a typo? 18V is an unusual value for a capacitor in one of these macs. Mouser also doesn't have a single cap with that value. No results.

 

[Powerbook27364]

Hmm. Strange. I'll add a note about it.

Sure. He won’t be able to get the values until tonight, but I’ll make sure just in case.

 

[3lectr1cPPC]

Alright, thanks.

 

[Powerbook27364]

Alright, thanks.

Oddly enough I found a listing on eBay but they are not smd. Mouser and digikey both show no results for me as well.

8pcs Panasonic EE 330mfd 18v 330uf 8x15mm audio electrolytic capacitor 105C | eBay

Find many great new & used options and get the best deals for 8pcs Panasonic EE 330mfd 18v 330uf 8x15mm audio electrolytic capacitor 105C at the best online prices at eBay! Free shipping for many products!

www.ebay.com

 

[3lectr1cPPC]

eBay caps can often be fake/knockoffs that are low quality. Those could also be NOS caps from 15 years ago, which you definitely don't want either. Apple's logic boards didn't often use uncommon values like that, and other sources point to 16V which makes more sense.

 

[Powerbook27364]

Just got confirmation, he misread it. It is indeed a 16v cap

 

[3lectr1cPPC]

Alright, good to know.

 

[Powerbook27364]

I just found a Facebook post from several years ago about recapping a duo 280, and it shows at least 3 of the caps match the 2300. The other caps aren't marked on the top , so I cannot determine the values of those. This supports your thought that they have the same values, so I will order those caps tonight.

 

[3lectr1cPPC]

Yeah, they seem to be the same. Good luck. Also, MacDat will be offline for the next 20 minutes or so. I'm pushing a full update to the server.

 

[Powerbook27364]

I saw on your website that there may be caps on the 250 inverter board. I will see if he can find the values if its not put back together. I also noticed your color classic page is missing psu/analog board as well as missing photos, so I may be able to help you out with that too since I have a color classic. My 280 has shipped out already so should take maybe 2 weeks before I have values and photos for that.

 

[3lectr1cPPC]

All sounds good. Main reason I don’t have any PSU values yet is because you often have to get proper high frequency or low esr stuff and values alone won’t do. You need the series of the original cap.